US Vice President Joe Biden on Wednesday implicitly criticised Palestinian leaders for not condemning attacks against Israelis, as an upsurge in violence marred his visit.

Six separate attacks took place shortly before or after Biden's arrival Tuesday, including a stabbing spree on Tel Aviv's waterfront by a Palestinian who killed an American tourist and wounded 12 other people.

The stabbings in the Jaffa port area took place as Biden met former Israeli president Shimon Peres about a kilometre (less than a mile) away.

Biden said his wife and grandchildren had been having dinner on the beach not far from the site of the stabbings.

"The kind of violence we saw yesterday, the failure to condemn it, the rhetoric that incites that violence, the retribution that it generates, has to stop."

Biden offered his condolences to the family of the American victim, 29-year-old Taylor Force, whom he noted had served in the US military in Afghanistan and Iraq.

Palestinian president Mahmud Abbas has repeatedly called for peaceful resistance against the Israeli occupation, but has not specifically condemned a wave of knife, gun and car-ramming attacks that erupted in October.

Islamist movement Hamas, which runs the Gaza Strip, often praises such attacks.

Biden held talks with Abbas later Wednesday in the West Bank town of Ramallah but they made no comments to reporters after the meeting.

A large number of the attackers have been young people, including teenagers, who appear to have been acting on their own.

The White House has said Biden would not be pursuing any major new peace initiatives during his visit despite the wave of violence.

Israel blames incitement by Palestinian leaders and media as a main cause of the violence, which has killed 188 Palestinians and 28 Israelis since October.

Most of the Palestinians were killed while carrying out attacks, Israeli authorities say.

Others were shot dead by Israeli forces during clashes or demonstrations.

Flare-up and Biden visit

The number of attacks had somewhat diminished recently and Israeli security forces were probing whether the flare-up was connected to Biden's visit.

On Wednesday, two young Palestinians, aged 19 and 21, shot at a bus from their car in an ultra-Orthodox Jewish neighbourhood of northern Jerusalem, police said.

A driver returned fire at the assailants before they fled.

Later they opened fire again just outside the Old City in annexed east Jerusalem, before police shot and killed the two assailants.

A 50-year-old man, thought to be a Palestinian from east Jerusalem, was seriously wounded.

Israeli authorities were investigating whether his injuries were the result of police or assailant gunfire.

In a separate attack, a 16-year-old Palestinian tried to stab Israeli forces at a checkpoint in the occupied West Bank and was shot dead, the army said.

As part of moves to curb the violence, Israel's government decided Wednesday "to complete immediately construction of the barrier around Jerusalem and build a new stretch" in a sector near the West Bank hotspot of Hebron, according to a government statement.

The United Nations humanitarian office OCHA, in a report published in September, said 64 percent of the barrier has already been built and it has isolated nine percent of Palestinian territory in the West Bank.

Talks overshadowed

Biden's visit had already been overshadowed by a new blow to the rocky relationship between US President Barack Obama and Netanyahu.

Netanyahu's decision not to accept an invitation for talks with Obama in Washington later this month "surprised" the White House, which first learned of it through news reports.

Both countries have been seeking to set aside their deep disagreement on the Iran nuclear deal, which Netanyahu strongly opposed, and show that ties between the two traditional allies remain strong.

They have been working on a new 10-year defence aid package for Israel, currently worth some $3.1 billion annually in addition to spending on projects such as missile defence.

Ahead of the Ramallah talks, senior Palestinian official Ahmed Majdalani said he was expecting "nothing" from Biden's visit.

"Mr. Biden is only coming to the region in the context of his plans regarding the fight against terrorism in Syria, not for us," he told AFP, referring to talks between Biden and Netanyahu on the Islamic State jihadist group.

Under heavy security, Biden made an unannounced stop Wednesday along with three of his grandchildren and his daughter-in-law at the Church of the Holy Sepulchre in Jerusalem's Old City.

The church is built at the site revered as the location of Jesus's crucifixion and tomb.